Merge pull request 'Globals and start.asm' (#19) from Gelthor/symphony_stdlib:graphics into main

Reviewed-on: TCShenanigans/symphony_stdlib#19

CONTRIBUTING.md

@@ -16,10 +16,22 @@ All functions in the standard library should follow the following outline:
 ; Arguments: <which register contains what argument>
 ; Result: <what is the result, and where is it stored>
 ; Clobbers: <list of registers that are clobbered>
+; Globals: <list of globals are accessed. OPTIONAL>
+; Errors: <list of any status codes returned in flags. OPTIONAL>
 <label>: <;SHOULD BE INLINED>
     <CODE>
 
 ```
 
 Functions should be in the appropriate asm file, if you are unsure where functionality fits make a seperate file and ask in the pull request
-Functions that are provided for convenience/reference but should be inlined in production code should be marked with `;SHOULD BE INLINED` after their label
+Functions that are provided for convenience/reference but should be inlined in production code should be marked with `;SHOULD BE INLINED` after their label.
+
+If the function returns a status code in flags, the preamble should list all it might return.
+
+## Globals
+
+Any function that uses global variables should document this in the preamble comment, see above.
+
+A file/module should check on intialisation that the address `globals.MAGIC_ADDRESS` contains the 16 bit value `globals.MAGIC_VALUE`, to ensure that the user has properly included [[src/start.asm]] and reservered the global variable area.
+
+No opinion is offered on whether modules can assume globals variables are initialised to zero.

README.md

@@ -3,7 +3,7 @@
 This is a standard library for symphony.
 It is both intended as a practical toolkit to develop more complex software as well as a teaching resource.
 
-If you just want to use the standard library [[src/stdlib.asm]] is your main header, include it after your code.
+If you just want to use the standard library [[src/stdlib.asm]] is your main header, include it after your code. Some modules also require [[src/start.asm]] at the very start of the program.
 
 If you are using it as a learning resource have a look at the [teaching folder](teaching).
 
@@ -20,7 +20,7 @@ If you are intersted in contributing have a look at [[CONTRIBUTING.md]]
 | preserved | sp, r8 - r12 |
 | scratch | flags, r1 - r7 |
 | arguments | r1 - r7 |
-| result | r1-r7 |
+| result | flags, r1 - r7 |
 | return address | r13 |
 
 Arguments not fitting into the 7 registers should be passed on the top of the stack, meaning they should be the last values pushed before the function call.
@@ -32,9 +32,14 @@ Should a function return more values than fit into the 7 registers, the caller h
 This reduces the amount of argument registers to 6 and all arguments above that shall go on the stack, the pointer to the result stack shall **always** be passed in an argument register.
 This register points at the highest available address for results, with the 8th result being stored there, the 9th below it and so on.
 
+Some functions return a success/failure status code in flags. A set low bit will indicate some error condition, the function may return more than one possible value to report different errors. A flags value of 0 is set on success. No other even values are used. This can be checked with `je` or `jne` immediatly on return to the caller. All other functions clobber flags.
+
 ### Stack
 Grows downwards from 0xXXFE_0000 (so top of memory -0x1_0000).
 
+### Globals
+Global variables are stored near the bottom of RAM in the address range 0x0010..0x0100. Programs should `include src/start` as the first line before their own code and before other includes, or otherwise reserve this space, the first instruction should be a jump to user code.
+
 ### Types
 
 #### String

src/errno.asm

@@ -0,0 +1,27 @@
+; Error numbers should be 16 bit ODD numbers, so they can be loaded as immediates
+; and can be checked with:
+;
+;   qcall falible_function
+;   jne falible_ok ; Jump no error
+;       ; handle error
+;   falible_ok:
+;   ; Happy path
+;   ; ...
+; OR
+;   qcall falible_function
+;   je handle_error ; Jump if error
+;   ; Happy path
+;   ; ...
+;   handle_error:
+;       ; handle error
+
+pub const OK                   = 0x0000
+pub const SCREEN_INVALID_MODE  = 0x0001
+pub const SCREEN_INVALID_WIDTH = 0x0003
+pub const SCREEN_FB_TOO_SMALL  = 0x0005
+pub const SCREEN_OUTSIDE_FB    = 0x0007
+
+pub const MAGIC_BAD            = 0x8001
+
+; Extended error codes, these would require loading a 32 bit value.
+pub const EXT_OK              = 0x00000000

src/globals.asm

@@ -0,0 +1,30 @@
+; Addresses of global variables
+
+pub const MAGIC_ADDRESS_LONG = 0x0c       ; U32 Location of the magic value
+pub const MAGIC_VALUE_LONG   = 0xb301534c ; U32 Full 32 bits of the magic value
+pub const MAGIC_ADDRESS      = 0x0e       ; U16 Location of the low 16 bits of magic value
+pub const MAGIC_VALUE        = 0x534c     ; U16 Low 16 bits of the magic value
+
+; If not double buffering these point to the same buffer
+; If double buffering they must the same size
+pub const FB_DISPLAY_PTR     = 0x10       ; U32 Currently displayed buffer
+pub const FB_DISPLAY_STRIDE  = 0x14       ; U16 Bytes in each row of the displayed buffer
+pub const FB_DISPLAY_DEPTH   = 0x16       ; U16 Bits per pixel of the display buffer
+pub const FB_DRAW_PTR        = 0x18       ; U32 Draw to this buffer
+pub const FB_DRAW_STRIDE     = 0x1c       ; U16 Bytes in each row of the draw buffer == FB_DISPLAY_STRIDE
+pub const FB_DRAW_DEPTH      = 0x1e       ; U16 Bits per pixel of the draw buffer == FB_DISPLAY_DEPTH
+pub const FB_SIZE_BYTE       = 0x20       ; U32 In bytes
+pub const FB_WIDTH_PX        = 0x24       ; U16 Width of screen in pixels
+pub const FB_HEIGHT_PX       = 0x26       ; U16 Height of screen in pixels
+
+; Log2 of width in pixels, e.g.
+; * 10 => 1024 * 768
+; *  8 =>  256 * 192
+pub const FB_LOG_WIDTH       = 0x28       ; U8
+pub const FB_LOG_STRIDE      = 0x29       ; U8 Log2 of FB_xxx_STRIDE in bytes
+
+pub const FB_BYTES_PER_PIXEL = 0x2a       ; U8 Specialisations should hardcode this
+; Log2 of bytes per pixel
+; * 0 => 8 bits per pixel
+; * 2 => 32 bits per pixel
+pub const FB_LOG_BPP         = 0x2b       ; U8 Specialisations should hardcode this

src/start.asm

@@ -0,0 +1,19 @@
+;@0 ; Reserve space for globals
+
+; First initialise the stack pointer
+nor sp, zr, 0xffff
+; Jump over the globals to user code
+jmp 0x100
+
+U32 0 ; 4 bytes
+
+; MAGIC_VALUE
+;@0x0c
+U32 0xb301534c
+
+; Pad with zeroes since the @addr feature is currently broken.
+; * https://discord.com/channels/828292123936948244/1545010596246847568
+;
+U1920 0  ; 240 bytes
+
+;@0x100 ; start of user code

src/stdlib.asm

@@ -3,6 +3,7 @@ pub include imath
 pub include array
 pub include console
 pub include mem
+pub include string_to_int
 
 ; Needs to be last!
 pub include LUTs

src/string_to_int.asm

@@ -0,0 +1,188 @@
+; Internal register assignments:
+; r1 - Partially parsed output integer
+; r2 - Parsing position
+; r3 - Character being parsed
+; r4 - Set to -1 if the input is negative
+
+; Convert string to integer (akin to libc atoi(), strotoi())
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+; Note: Unless the input is "0", tail-calls into a base-specific specialization.
+pub auto:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne auto_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+auto_positive:
+load_16 r3, [r2]        ; 2-byte prefix "0b", "0o", "0x", etc.
+or r3, r3, 0x20         ; 2nd char to lower case
+add r2, r2, 2
+cmp r3, 0x3062 ; "0b"
+je bin_loop
+cmp r3, 0x306F ; "0o"
+je oct_loop
+cmp r3, 0x3078 ; "0x"
+je hex_loop
+sub r2, r2, 2           ; no matching prefix, move pointer back
+jmp dec_loop
+
+; Epilogue
+done:
+add r1, r1, r4          ; If r4 is -1, negate r1. Else it's 0 and no effect.
+xor r1, r1, r4
+mov flags, 0            ; No error
+jmp r13
+
+; Convert decimal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub dec:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne dec_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+dec_loop:
+load_8 r3, [r2]
+dec_positive:
+sub r3, r3, 0x30 ; '0'
+cmp r3, 9
+ja done
+add r2, r2, 1
+lsl flags, r1, 2        ; Use flags to help multiply by 10
+add r1, r1, flags
+lsl r1, r1, 1
+add r1, r1, r3
+jmp dec_loop
+
+; Convert binary string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub bin:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne bin_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+bin_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x3062 ; "0b"
+jne bin_loop
+add r2, r2, 2
+bin_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 1
+ja done
+add r2, r2, 1
+lsl r1, r1, 1
+add r1, r1, r3
+jmp bin_loop
+
+; Convert octal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub oct:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne oct_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+oct_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x306F ; "0o"
+jne oct_loop
+add r2, r2, 2
+oct_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 7
+ja done
+add r2, r2, 1
+lsl r1, r1, 3
+add r1, r1, r3
+jmp oct_loop
+
+; Convert hexadecimal string to integer
+; Arguments:
+; r1 - Pointer to string
+; Result:
+; r1 - Parsed integer
+; r2 - Pointer to first rejected input byte
+; Clobbers:
+; flags
+; r3 - last character read
+; r4 - Negative marker
+pub hex:
+mov r2, r1
+mov r1, 0
+mov r4, 0
+load_8 r3, [r2]
+cmp r3, 0x2D ; '-'
+jne hex_positive
+sub r4, zr, 1           ; Set r4 to -1
+add r2, r2, 1
+hex_positive:
+load_16 r3, [r2]        ; check for prefix
+or r3, r3, 0x20         ; 2nd char to lower case
+cmp r3, 0x3078 ; "0x"
+jne hex_loop
+add r2, r2, 2
+hex_loop:
+load_8 r3, [r2]
+sub r3, r3, 0x30 ; '0'
+cmp r3, 10
+jb hex_add
+sub r3, r3, 0x11 ; 'A' - '0'
+and r3, r3, 0xdf        ; to lower case
+cmp r3, 5               ; 0-5: 6 letters
+ja done
+add r3, r3, 10          ; Adjust for digits below
+hex_add:
+add r2, r2, 1
+lsl r1, r1, 4
+add r1, r1, r3
+jmp hex_loop

tests/string_to_int_test.asm

@@ -0,0 +1,57 @@
+; test harness for string_to_int
+; Registers:
+; r8 - test address
+; r9 - expected result
+; r10 - actual length
+; r11 - expected length
+li r8, tests
+li r12, end_of_tests
+next_test:
+; Set up arguments and run test
+add r1, r8, 5          ; Start of test string
+mov r13, atoi_test_ret
+jmp stdlib.string_to_int.auto
+atoi_test_ret:
+
+; Load reference data
+load_32 r9, [r8]       ; Expected result
+sub r10, r2, r8
+sub r10, r10, 5        ; Actual string length
+add r11, r8, 4         ; Address of expected length
+load_8 r11, [r11]      ; Expected length
+
+; Verify results
+cmp r1, r9
+incorrect_result: jne incorrect_result
+cmp r10, r11
+incorrect_length: jne incorrect_length
+
+; Next test
+add r8, r8, 0x10
+cmp r8, r12
+jl next_test
+
+; Done
+success: jmp success
+
+include ../src/stdlib
+
+@0x20000
+tests:
+; inlen is the number of input bytes the function is expected to consume
+; addr  result          inlen  instr
+@0x20000 U32 0           U8 0   "\0"
+@0x20010 U32 0           U8 1   "0\0"
+@0x20020 U32 1           U8 1   "1\0"
+@0x20030 U32 2           U8 1   "2:\0"
+@0x20040 U32 42          U8 2   "42\0"
+@0x20050 U32 67          U8 2   "67lol\0"
+@0x20060 U32 0x69a       U8 5   "0x69a@\0"
+@0x20070 U32 0x4B4       U8 5   "0x4B4g\0"
+@0x20080 U32 0o23        U8 4   "0o239\0"
+@0x20090 U32 0b1011      U8 6   "0b1011\0"
+@0x200a0 U32 0b10001     U8 7   "0b100012\0"
+@0x200b0 U32 0xFFFFFFEB  U8 3   "-21\0"       ; Yuk
+@0x200c0
+end_of_tests:
+